The present invention relates to a coupling arrangement for coupling together rail vehicles such as railway carriages and locomotives, consisting of a coupling head comprising a coupling housing joined to the rail vehicle and having an active coupling device in the form of a plunger movable between an outer and an inner position and designed to co-operate with a similar plunger in a corresponding coupling head when two coupling heads are coupled together.
In automatic coupling of rail vehicles such as railway carriages, locomotives and the like, coupling arrangements are used that permit carriages, etc. to be coupled together regardless of which end of the carriage is facing the carriage with which it is to be coupled. Such coupling arrangements comprise a coupling housing connected to the rail vehicle and having an active coupling member in the form of a plunger designed to co-operate with a similar plunger in a corresponding coupling head when these are coupled together. Each plunger has a surface that is inclined to the longitudinal direction of the coupling head and a load-absorbing contact surface perpendicular to this direction. When the two coupling heads are united, the inclined surfaces are brought into contact with each other, whereupon the plungers are displaced in opposite directions until the two contact surfaces have been aligned so that the plungers can return and be brought into engagement with each other. Such a coupling arrangement is manufactured by SAB WABCO BSI Verkehrstechnic GmbH, Germany.
The disadvantage with the known coupling arrangement is that, after some time in use, the load-absorbing contact surfaces of the plunger, as well as other components in the coupling head, become worn. Railway tracks are usually not so smooth that carriages and locomotives can be driven along them without vibration and twisting, which subject the coupling heads to considerable strain. It has been found that coupling heads that have been subjected to a certain amount of wear lose their load-transmitting function when subjected to such strain, i.e. the plungers lose their grip on each other. The connection between carriages or between carriage and locomotive is consequently broken and the train unit is automatically braked and comes to a standstill. Other reasons for such coupling heads losing their function are that the spring retaining the plunger in engagement position breaks or becomes fatigued, or that two plungers do not achieve correct engagement with each other. Since this type of automatic coupling arrangement is widely used, a great need exists to improve its function as regards ensuring that the coupling heads do not unintentionally separate during use.
The object of the present invention is to provide a coupling arrangement that does not have the drawbacks of the existing coupling arrangement described above. The object is achieved with a coupling arrangement consisting of a coupling head comprising a coupling housing joined to the rail vehicle and having an active coupling device in the form of a plunger movable between an outer and an inner position and designed to cooperate with a similar plunger in a corresponding coupling head when two coupling heads are coupled together. The plungers are movable in directions that are substantially perpendicular to the longitudinal directions of the coupling heads and can be moved away from each other by mutual contact at interlocking, and with the aid of a disengaging means for each plunger when a train unit is being uncoupled.
To prevent the plungers being unintentionally separated when their contact surfaces have become worn to a certain extent, or when rupture or fatigue occurs in the plunger springs, a locking device is provided in each coupling arrangement and comprises a locking member arranged to be brought into contact with the plunger when this is in its outer position and to prevent the plunger being displaced from this position.
In a preferred embodiment of the invention the locking arrangement is provided with a toggle joint comprising two locking links which are hingeably joined and placed in a locking housing and which, when the plunger is in locked position, are aligned in one and the same plane, the outer part of one link resting against the locking housing and the outer part of the other link resting against the locking member, thus transmitting a force between the locking member and the locking housing. The locking links can be turned in relation to each other and folded about a hinge so that their outer ends are moved towards each other. When the locking links are folded in this manner their force-transmitting influence on the locking member ceases and the latter can therefore be disengaged from its contact with the plunger so that this is released.
The locking member may consist of a roller which, upon locking, is displaced directly or indirectly at right angles to its longitudinal direction in a channel in the locking housing in a direction towards the plunger to engage with a corresponding recess in its outer shell.
With the object of being able to operate the locking arrangement between locked and disengaged position an actuating rod is arranged to extend through the locking arrangement and is connected to the locking links. One end of the actuating rod is connected to a piston in an operating cylinder which, when pressurised by means of a hydraulic or pneumatic pressure medium, causes the locking links to press the locking member to engagement with the plunger.
However, the invention is not limited to a locking arrangement comprising a toggle joint and many embodiments are feasible instead.
In a first alternative embodiment of the locking arrangement in accordance with the invention, the locking member may be influenced by a linearly movable wedge, which, upon contact, presses the locking member against the plunger. The wedge is connected to an actuating rod of the type described above.
In a second alternative embodiment of the locking arrangement in accordance with the invention the locking member may consist of a rod activated by a servo device e.g. a compressed air cylinder, with the aid of which the rod can be inserted into a hole in the plunger when this is in its outer position, thereby locking the plunger against undesired depression. The servo device is only activated after connection has been performed so that the rod engages with the plunger. The rod may be spring-loaded and returns to its original position as soon as the servo device is disconnected. Alternatively the rod may be spring-loaded in the starting position and automatically engage with the plunger when this is pressed in, and is disengaged with the aid of the servo device.
In a third alternative embodiment of the locking arrangement in accordance with the invention the locking member may consist of a latch that can be turned between a disengaged position in which the plunger is freely movable, and a locked position in which the latch is in communication with a recess in the plunger. The latch can be actuated by a servo device in the same way as for the rod as mentioned above.
In a fourth alternative embodiment of the locking arrangement in accordance with the invention the locking member may consist of a turnable rod that extends through a recess in the shell of the plunger, the rod having a recess extending to its centre. When the rod is turned so that its recess is directed towards the plunger the latter can move freely, but when the rod is turned so that its solid part is in communication with the recess in the plunger the latter is locked. This turnable rod can be actuated by a servo device.
Additional alternative solutions as regards the design of the locking arrangement are feasible within the scope of the invention, which relates to all forms of locking members that can be brought into contact with and firmly retain the plunger when this is in its outer position, and prevent the plunger, due to wear, broken or fatigued springs and the like, releasing its grip on the plunger in the corresponding coupling head. The choice of solution as regards the locking member is determined to a certain extent by the design of the rest of the coupling arrangement and how much space is available for the locking arrangement, which in turn is determined by the demands placed on its function.